Py Concentration Research Articles

Study of Chemical Polymerization of Polypyrrole with SDS Soft Template: Physical, Chemical, and Electrical Properties.

Polypyrrole (PPy) is a conductive polymer known for its biocompatibility and ease of synthesis. Chemically polymerized PPy was synthesized in the presence of sodium dodecyl sulfate (SDS), showing correlations among chemical properties, physical morphology, and electrical properties. Focused synthesis parameters included the pyrrole (Py) concentration, SDS concentration, and ammonium persulfate (APS)/Py ratio. The addition of SDS during chemical polymerization influenced the physical morphology of PPy by altering the self-assembling process via micelle formation, yielding sheet-like morphologies. However, the phenomenon also relied heavily on other synthesis parameters. Varying SDS concentrations within the 0.01 to 0.30 M window produced PPy sheets with no significant difference in optical band gap or physical size. While using 0.10 M SDS, an increase in Py concentration from 0.10 to 0.30 M yielded a larger size of PPy as the morphology changed from sheet-like to irregular shape. The band gap dropped from 2.35 to 1.10 eV, and the conductivity rose from 6.80 × 10-1 to 9.40 × 10-1 S/m. With an increase in the APS/Py ratio, the PPy product changed from a random to a sheet-like form. The product provided a larger average size, a decreased band gap, and increased electrical conductivity. Py polymerization in the absence of SDS revealed no significant change in shape or size as the Py concentration increased from 0.10 to 0.30 M; only a sphere-like form was observed, with a large band gap and small conductivity. Results from Raman spectral analysis indicated a correlation between optical band gap, physical morphology, and bipolaron/polaron ratio, mainly at the wavelengths associated with C-C stretching and C-H deformation. The increase in average size was associated with a decrease in band gap and resistance as well as an increase in the bipolaron/polaron ratio. This work indicates a strong correlation between size, morphology, electrical properties, and the bipolaron/polaron ratio of PPy in the presence of SDS.

Polypyrrole Modified Carbon Nanotube/Polyimide Electrode Materials for Supercapacitors and Lithium-ion Batteries

Lithium-ion batteries have evolved and transcended in recent years to power every device across the spectrum, from watches to electrical vehicles and beyond. However, the lithium-ion battery requires the use of heavy and expensive transition metal oxides that have limited life cycles. Conductive polymer nanocomposites have been shown to possess good electrochemical and thermomechanical properties and are considered to be effective alternatives to transition metal oxides. The fabrication and properties of polyimide matrix-single wall carbon nanotube, SWCNT composite electrode materials, modified by the electrodeposition of polypyrrole, PPy was successfully carried out. The doping of PPy with p-Toluene sulfonic acid, T resulted in a dramatic transformation of the morphology and specific capacitance of the electrode material. Electrochemical impedance spectroscopy, EIS, cyclic voltammetry, CV, and galvanic charge–discharge tests were used to measure the electrode’s specific capacitance and specific capacity. Maximum specific capacitance values of up to 84.88 F/g and 127.13 F/g were obtained by CV and charge–discharge tests, respectively. A capacitance retention of over 80% was obtained after over 500 cycles of testing. The insertion of doped PPy into the electrode material by electrochemical polymerization was shown to positively correlate to the improved electrochemical performance of the nanocomposite. An increase in the porosity of about 34.68% over the non-doped polypyrrole was obtained from EIS measurement and supported by the optical microscope pictures. Increasing the process parameters, such as pyrrole, Py concentration and the amount of dopants, lead to a dramatic increase in the specific capacitance and capacity of the composite electrodes.

Enhanced Electrochemical Performance of Nanocellulose/PPy·CuCl2 Electrodes for All-Cellulose-Based Supercapacitors

Supercapacitive devices using a bacterial nanocellulose (BNC)-based separator and electrodes, providing mechanical support with high surface area while allowing the permeability of ions and avoiding short circuits, have been assembled and characterized. For the electrodes, BNC membranes were incorporated with polypyrrole (PPy) at different concentrations using copper chloride as oxidizing agent. As the separator, pure nanocellulose membranes were used. Scanning electron microscopy analysis revealed that increasing the pyrrole concentration from 0.04 mol/L to 0.08 mol/L and the molar ratio of oxidizing agent to monomer (CuCl2:Py) from 2:1 to 4:1 resulted in a uniform BNC coating. Symmetrical supercapacitor devices were assembled and subjected to cyclic voltammetry, charge–discharge measurements, and cycle stability testing. A maximum specific capacitance value of 1789 mF/cm2 was extracted from the voltammetry curves for the device constructed using the membrane with the highest Py concentration and oxidizing agent-to-monomer ratio. The best power density and energy density values obtained during discharge testing at 1 mA/cm2 were 5.47 mW/cm2 and 187 μWh/cm2, respectively. These promising results confirm the feasibility of using BNC as both the separator and electrodes when building supercapacitors.

One‐Step Synthesis of Conductive BNC/PPy·CuCl2 Hybrid Flexible Nanocomposites by In Situ Polymerization

This work reports the one‐step synthesis of bacterial nanocellulose (BNC) incorporated with polypyrrole (PPy) by chemical in situ polymerization of pyrrole (Py) using CuCl2·2H2O as both oxidant agent and functional component, varying the concentration and molar ratio. Electrical, morphological, and physical‐chemical properties of these nanocomposites were investigated. The results revealed that with the increase of Py concentration and molar ratio, the nanocomposites presented traces of copper chloride and copper oxide as shown by Raman and XRD analysis. The quality of bacterial cellulose nanofibers coating by the polymer and the electrical conductivity of the nanocomposites was directly affected by those variables. The combination of the conducting polymer with the oxidant agent offers possibilities for different applications such as electronic devices and sensors.

Preparation and properties of electro-conductive fabrics based on polypyrrole: covalent vs. non-covalent attachment

Electro-conductive fabrics were prepared via in situ oxidative polymerization of pyrrole (Py) in the presence of unmodified and chemically modified cotton fabrics. Chemical modification of cotton fabric was achieved by covalent attachment of a bifunctional linker molecule to the surface of the fabric, followed by incorporation of a monomer unit onto the linker. The fabrics were characterized using Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron spectroscopy, and thermal analysis. Furthermore, the effect of Py concentration on the degree of polypyrrole (PPy) grafting, surface morphology, electrical resistivity, and laundering durability were studied for both types of cotton fabrics. Reductions of several orders of magnitude in surface and volume electrical resistivities were observed for both non-covalently and covalently linked cotton-PPy systems, whereas the effect of covalent pre-treatment of the fabric was stronger at low Py concentration. On the other hand, at higher monomer concentration, the electrical properties and laundering durability of the fabrics we comparable for both unmodified and chemically pre-treated cotton fabrics, indicating that only a small fraction of PPy chains were chemically grafted onto the fabric surface with the majority of the polymer being connected to the fabric through hydrogen bonds.

Core-shell structure of polypyrrole grown on W18O49 nanorods for high performance gas sensor operating at room temperature

In this work, uniform core-shell structure of polypyrrole wrapped on tungsten oxide nanorods (PPy@W18O49 core-shell nanorods) were synthesized via a two-step process for gas-sensing applications. The core-nanorods of W18O49 were first grown by solvothermal method with tungsten hexachloride (WCl6) as precursor. The PPy-shell layer was then formed uniformly on the solvothermally synthesized W18O49 nanorods by in-situ chemical polymerization of pyrrole monomer (Py), with sodium dodecyl benzene sulfonic acid (DBSA) as dopant and ammonium persulfate (APS) as oxidant. High dispersion of Py achieving in ethanol is proved to be crucial to form the uniform PPy-shell layer, and the layer thickness of PPy-shell is highly controlled by adjusting the Py concentration in polymeric solution. The morphology and structure of the nanocomposite were characterized systematically; it shows that the composite exhibits perfect core-shell structure of one-dimensional (1D) nanorods with average diameter of around 70–90 nm. The NH3-sensing properties of the sensors based on the PPy@W18O49 core-shell nanorods were investigated at operating temperature of 15–130 °C over NH3 concentration ranging from 1 to 200 ppm. The response magnitude of the PPy@W18O49 sensor can be affected seriously by temperature fluctuation, even in room temperature range (15–30 °C), and meanwhile, a temperature-dependent p-n response characteristic reversal is observed for the heteronanorods sensor. At much low room temperature of 15 °C, the present PPy@W18O49 nanorods show quick and sensitive response to NH3 gas mainly due to the ultrathin, uniform PPy shell and the special heterojunction effect between p-type PPy and n-type W18O49. The underlying gas-sensing mechanism is analyzed.

Evaluation of chemical synthesis of polypyrrole particles

Abstract π-π conjugated polymer polypyrrole (PPy) particles were synthesized by chemical oxidative polymerization of pyrrole (Py) monomers using H2O2 as an oxidant. No surfactants were added to the polymerization solution, therefore pure PPy particles were formed. UV–vis molecular absorption spectroscopy (UV–vis MAS) was used to monitor the Py polymerization process. The spectral properties and morphology of formed PPy particles were studied using Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The influence of H2O2 and Py concentration, temperature and pH of media on the PPy particles formation rate was investigated. It was found that the polymerization solutions were unstable colloidal suspensions consisting of the PPy particles. SEM analysis revealed that PPy particles were 50–100 nm in diameter, which aggregated into larger structures of 600–1000 nm in diameter with irregular granular morphology. FTIR data showed that the molecular structure of the synthesized particles was identical to that of PPy produced by conventional methods.

Conductive polypyrrole/viscose fiber composites

Polypyrrole (PPy) was polymerized with pyrrole (Py) as the monomer, FeCl3 as an oxidant and sodium dodecyl benzene sulfonate (SDBS) as the dopant on the surface of viscose fiber (VCF) to prepare the conductive PPy/VCF composites. Fourier transform infrared spectra (FT-IR), thermal gravimetric analysis (TGA) and X-ray photoelectron spectroscope (XPS) proved that the interaction between PPy and VCF formed in the PPy/VCF composites. Three structures of N atoms (imine, amine and cationic atoms) were found in PPy of PPy/VCF composites. The influence of reaction conditions including reaction time, Py concentration, FeCl3 concentration and SDBS concentration on the morphology and the conductivity of PPy/VCF composites was investigated in detail. The orthogonal experiments were designed to determine the optimal reaction conditions: reaction time 5h, Py concentration 0.1mol/L and FeCl3 concentration 0.25mol/L. When PPy/VCF composite was washed 50 times in water, the conductivity still kept at 1.5S/cm, and this value was stable for more washing.

Synthesis of Conductive PPy/SiO2 Aerogels Nanocomposites by In Situ Polymerization of Pyrrole

Electrical conductive nanocomposite aerogels were synthesized through in situ oxidative polymerization of pyrrole (Py) using ammonium persulfate (APS) as an oxidizing agent in SiO2 gels. The effect of Py concentration on the electrical conductivity and physical and morphological properties of aerogels SiO2/PPy was evaluated. B.E.T. analysis indicated that the surface area of the composite SiO2/PPy decreases with increasing concentration of Py. CHN analysis showed an increase in the amount of PPy, from 13 wt.% to 23 wt.%, with increasing concentration of pyrrole synthesis. FTIR‐ATR analysis of the composites revealed bands in the region of 1500–1400 cm−1, indicating the presence of the conductive polymer in the silica aerogel as well as the characteristic bands of Si‐O‐Si and Si‐OH covalent bonds. TEM micrographs revealed the presence of particles of PPy with the increased size of the nanoparticles. The composites were successfully applied as passive components, in RC circuits, for low‐pass frequency filters. The filters exhibited a cutoff frequency at approximately 435 Hz. The aerogels obtained in this work exhibited suitable electrical conductivity for use in various other applications in electronics.

Facile synthesis of high density polypyrrole nanofiber network with controllable diameters by one step template free electropolymerization for biosensing applications

In this paper, we report fabrication of enzymatic glucose biosensor based on growth of high density polypyrrole (PPy) nanofiber network using one step template free electropolymerization method. PPy was grown potentiostatically on gold coated glass substrates. Significant changes in the sensing response were observed for biosensors fabricated with different concentrations of pyrrole (Py) monomer and polymerization potentials. Among the fabricated biosensors, the highest sensitivity of 1.9mAcm−2M−1, with a wide range of linear operation (125μM–11.25mM) was observed for 0.15M Py concentration and 0.8V polymerization potential. The observed results indicate that low monomer concentration and moderately low polymerization potential is highly suitable for growth of PPy nanofiber network with controllable fiber diameters having high aspect ratio, resulting in high sensitivity for biosensor application.

Development of a novel pressure sensing material based on polypyrrole-coated electrospun poly(vinylidene fluoride) fibers

Abstract Conductive polypyrrole-coated poly(vinylidene fluoride) (PVDF/PPy) fibers with diameters ranging from 500 nm to 1 μm were prepared through pyrrole (Py) oxidative polymerization on electrospun PVDF membrane. The influence of polymerization conditions on structures and properties of PVDF/PPy composites were investigated. The electrical conductivity and PPy content enhanced significantly with increasing Py concentration due to the conducting polymer layer formation that completely coated the PVDF fiber surfaces. The effect of dynamic load on electrical conductivity of PVDF/PPy composites has been registered. The maximum electrical sensitivity was observed for the composites containing 50 wt.% of PPy content, for which the relative conductivity increases around 40-fold with applied compressive stress. This behavior can be explained by the fact that during compressive stress, the contact between PVDF/PPy fibers increases to form new conducting pathways and, hence, the relative conductivity of the polymer composites enhances significantly. It was also observed that the electrical conductivity is almost the same as its previous value after the loading being released. The PVDF/PPy composite properties produced by the method described in this study have showed interesting possibilities for pressure sensor developments.

Polycyclic aromatic hydrocarbons (PAHs) in fine and coarse particles

<p>About 140 samplings of fine and coarse particles were gathered during the year 2006 in Kozani that represent an urban area surrounded by opencast coal mining. A low volume dichotomus sampler has been used to trap suspended particles. The filters used were teflon, which are ideal for analysis in the determination of PAHs. The determination of Polycyclic Aromatic Hydrocarbons (PAHs) has been carried out by the use of the analytic technique of large volume injection and gas chromatography – mass spectrometry (LVI - GC/MS). The extraction of substances has been made in a two stage procedure, firstly with agitation in a magnetic shaker and secondly by the use of ultrasonic bath. This technique has given high recoveries of PAHs, in short time intervals. The mean daily concentrations of fine particles varied from 4 to 48 μg m-3 and annual mean was 16 μg m-3. The mean daily concentrations of coarse particles respectively varied from 2 to 67 μg m-3 with 23 μg m-3 annual mean concentration. The ΣPAH concentrations for fine samples were 4.80 ± 7.06 ng m-3 and for coarse samples were 1.36 ± 1.59 ng m-3. The mean B[a]Py concentration for fine particles was 0.38 ng m-3. Finally, diagnostic ratios were used to characterize and identify PAHs emission source in this study.</p>

Conducting polypyrrole‐coated banana fiber composites: Preparation and characterization

AbstractIn this study, conducting banana fibers (BF) were obtained through in situ oxidative polymerization of pyrrole (Py) on the BF surface using ferric chloride hexahydratate (FeCl3·6H2O) as an oxidant. Suitable reaction conditions are outlined for the polymerization of Py: oxidant/monomer molar ratio, Py concentration and polymerization time of 2/1, 0.05 mol.L−1 and 30 min, respectively. Under these conditions, high‐quality conducting fibers containing polyPy and BF (PPy‐BF) were obtained with an electrical resistivity as low as 0.54 Ω.cm. The PPy‐BF was blended with different concentrations of polyurethane (PU) by mixing the two components in a vacuum chamber and then applying compression molding. The electrical resistivity of composites with 25 wt% of PPy‐BF was around 1.8 × 105 Ωcm, which is approximately 108 times lower than that found for pure PU. Moreover, PU/PPy‐BF composites exhibited higher mechanical properties than pure PU and PU/PPy, indicating that these conducting fibers can also be used as reinforcement for polymer matrices. The properties of the PPy‐BF obtained by the method described herein open interesting possibilities for novel applications of electrically conducting fibers, from smart sensors to new conducting fillers that can be incorporated into several polymer matrixes to develop conducting polymer composites with good mechanical properties.POLYM. COMPOS., 2013. © 2013 Society of Plastics Engineers

Anisotropic fluorescence materials: Effect of the synthesis conditions over the incorporation, alignment and aggregation of Pyronine Y within MgAPO-5

In order to prepare a highly fluorescent anisotropic material, different hydrothermal synthesis conditions have been studied in an attempt to favor the incorporation of the fluorescing dye Pyronine Y as monomeric species within the large-pore nanoporous aluminophosphate MgAPO-5 (AFI-type structure) during its crystallization (one-pot synthesis). Valuable information regarding the dye orientation, molecular distribution and aggregation behaviour inside the nanochannels of MgAPO-5 as a function of the gel composition has been obtained using the FLIM technique (Fluorescence Lifetime Imaging Microscopy). DFT-based calculations of the different dye species occluded within the nanochannels of MgAPO-5 allowed us to explain the properties of the newly synthesised composite materials. Our results show that although H-aggregates can fit within the MgAPO-5 channels, their presence can be reduced by varying the synthesis parameters, in particular by decreasing the template and PY concentration and increasing Mg content.

Neuronal cells’ behavior on polypyrrole coated bacterial nanocellulose three-dimensional (3D) scaffolds

In this work, polypyrrole (PPy) was in situ polymerized onto the surface of bacterial nanocellulose (BNC) produced by Gluconacetobacter xylinus, by chemical oxidation in aqueous medium using ammonium persulfate. Composites (BNC/PPy) were produced with varying concentrations of pyrrole (Py). The produced BNC/PPy membranes were used as a template for the seeding of PC12 rat neuronal cells. Cell suspensions were directly seeded onto the surfaces of the BNC/PPy membranes. The Py concentration affected the behavior of neuronal cells that adhered and grew significantly more on BNC/PPy comparatively to BNC. Scanning electron microscopy (SEM) micrographs revealed that PC12 cells adhered on the surface of the BNC and BNC/PPy membranes. Conductive PPy coatings on nanofibers acting as an active interface for tissue engineering may be used to regulate cell activity through electrical stimulations.

Preparation and Properties of Waterborne Cationic Polyurethanes/Polypyrrole Conductive Composites

A series of waterborne cationic polyurethanes dispersions (CWPU) was prepared through prepolymerization method by reacting polyethylene glycol (PEG1000) and isophorone diisocyanate (IPDI) with N-methyl diethanol amine (MDEA) as chain extender. Then FeCl3 was employed as oxidant, therefore CWPU/polypyrrole (CWPU/PPy) conductive composite was prepared by in situ chemical oxidative polymerization of pyrrole (Py) in CWPU dispersions. Effects of molar ratio of FeCl3 to Py, Py concentration on the resistivity of the CWPU/PPy composite films were investigated. The structure, morphology and thermal stability were also characterized by Fourier infrared spectra (FT-IR), light scattering, TEM, and TGA. FT-IR demonstrated the presence of hydrogen-bonding interactions between CWPU and PPy. The average particle size of CWPU/PPy increased from 10.61nm to 30.29nm compared with pure PU, and corresponding size distribution decreased from 0.850 to 0.346. It was also found that CWPU/PPy displayed as spherical morphology, and no aggregation among particles was detected among particles. TGA certified CWPU/PPy was endowed with better thermal stability. In addition, conductivity stability of composites films was also studied. It was found that composite films not only displayed low resistivity but also improved conductivity stability.

Chemical in situ polymerization of polypyrrole on bacterial cellulose nanofibers

Conducting porous nanofibrous composite membranes of bacterial cellulose (BC) and polypyrrole (PPy) were prepared through in situ oxidative chemical polymerization of pyrrole (Py) on the surface of synthetized BC nanofibers by using FeCl3 as oxidant agent. The influence of polymerization conditions on electrical conductivity, morphological and thermal stability of the BC/PPy composites was investigated. The amount of PPy deposited on the BC nanofibers increased with increasing the monomer concentration and reaction time while the electrical resistivity of the composites decreased due to the formation of a continuous layer that coated the nanofiber surface. Fourier transform infrared (attenuated total reflectance mode) spectroscopy (FTIR-ATR) of the composites revealed strong interaction between PPy and BC, as characterized by a blue-shift of C–N band of PPy towards pure PPy with increasing Py concentration. BC/PPy composites showed higher thermal stability than BC membrane due to the protective effect of the conducting polymer coating. Scanning electron microscopy (SEM) analysis of the composites revealed that PPy consisted of particles of mean size of 35nm that form a continuous coating that fully encapsulates the BC nanofibers. The material properties obtained by the method described in this work for the BC/PPy composites open interesting possibilities for novel applications of electrically conducting bio-based composites, particularly those that may exploit the biocompatible nature of the BC/PPy membranous composite.

Electrospun Nanofibers of Polypyrrole-Poly(Acrylonitrile-co-Vinyl Acetate)

The oxidative polymerization of pyrrole (Py) by cerium(IV) on Poly(Acrylonitrile- co-Vinyl Acetate) matrix was performed. Nanofibers were obtained from this solution by the electrospinning method. A new absorption band was observed corresponding to the CH in plane vibration of polypyrrole (PPy) by Fourier transform infrared-attenuated total reflectance spectrophotometric analysis. A linear relationship was determined between the absorbance ratios of functional groups corresponding to the conjugated polymeric units and initial Py concentrations in the presence and absence of Py. Scanning electron microscope images indicated that the diameters of nanofibers were dependent on PPy content and that the average nanofiber diameters were reduced with increasing the initially added Py concentration. The alternating current conductivity of nanofibers was increased with frequency, particularly in the higher frequency region (> 105 Hz).

Unique fluorescence spectra of a disubstituted pyrene surfactant in Langmuir–Blodgett films

We first observed a unique pyrene (Py) emission from 10-(1-(6-hexyl)pyrenyl)decanoic acid (1,6-HPDA) Langmuir–Blodgett (LB) films. In the fluorescence spectra of the 1,6-HPDA LB films, the normal bands of monomer and excimer emission of Py were absent but the new structured emission band with peaks at 422, 448, and 473 nm was observed. Besides the intensity, the shape of the characteristic structured emission band at shorter wavelengths than normal excimers did not changed essentially on lowering the Py concentration in the LB monolayer from 100 to 1 mol%. The spectroscopic studies on HPDA LB films of a variety of Py concentrations suggested that a novel excimer responsible for the structured new emission would be efficiently formed by photo-excitation of a Py–Py pre-associated dimer in different manners than those of normal excimer formations.

The reaction of [bispyridinotetrakis(t-butyl)phthalocyaninato]iron(II) with dioxygen to give μ-oxo-bis[tetrakis(t-butyl)phthalocyaninato]iron(III)

The reaction of [bispyridinotetrakis(t-butyl)phthalocyaninato]iron(II), ( py )2 FePc t, with dioxygen in CH 2 Cl 2, gives almost quantitatively the oxo-bridged μ-oxo-bis[tetrakis(t-butyl)phthalocyaninato]iron(III) as the final, stable product. The reaction order with respect to the starting complex changes within a run. For t = 0, the rate is proportional to the ratio [Formula: see text] (Equation 1) where y0 is the initial absorbance of the solution and a1 and a2 are linear functions of [O2]. For t > 0, the instantaneous rate is instead described by the equation Rate = b [O2][A]/([A]0 - [A]) (Equation 2), where A is ( py )2 FePc t and the coefficient b is again proportional to [ O 2]. A mechanism is proposed implying the presence of trace amounts of ( py )(S) FePc t (S = axially bound CH 2 Cl 2) in equilibrium with ( py )2 FePc t. Both species are able to generate the transient pentacoordinate ( py ) FePc t that may react with py and S, giving back the hexacoordinate precursors, or with dioxygen, giving ultimately the μ-oxo complex. At t = 0, the species ( py )(S) FePc t, expected to be much more labile than ( py )2 FePc t, is at its maximum concentration and is assumed to give the prevaling contribution to the instantaneous rate. As the reaction proceeds, and free pyridine accumulates in the solution, the concentration of ( py )(S) FePc t decreases rapidly and the transient ( py ) FePc t is produced essentially by the bispyridino complex. This fact and the still growing concentration of free pyridine account for the Equation 2. Finally, when the py concentration is buffered by addition of small amounts of base, the reaction attains a simple first order law. Present data further support the iron(III) formulation of the final μ-oxo product and are inconsistent with the iron(II) hypothesis put forward by some authors.